As you journey throughout Terraria, you may encounter special types of weapons. Certain summoning staffs, or special items, will summon an invincible attacking ally that will target your opponents. While it can sound enticing to have all the work done for you, summoners can face other unique challenges in Terraria.
These minions can be summoned in large groups with summoner-appropriate armor and buffs. However, you can always have at least one minion summoned regardless of your summoning capabilities. You can look into summoning minions if you need just a little extra support.